Knives have been disclosed with blades having pivotal "U"-section handles that extend back-to-back from one end of the blade where they are detachably held together at the free ends to act as a single handle for the exposed blade, and that pivot from that position to a face-to-face position between them encasing the blade for safe storage. Swinging loops have been used for attaching the free ends of the handles, and, in the inventions of the present inventor, pivotal blocks that serve additional uses.